X ILLUSTRATIONS. 



Page. 

 Pi-ATK XIX. Thin sections from the Quartz-slate member 486 



Fig. 1. Biotitic chlorite-slate.. 



Fig. 2. Biotite-slat.'. 



Fig. 3. Sandstone. 



Fig. 4. Argillaceou.s .shale. 



XX. Thin .seftions from the ni>)>c'r horizon of the Qnartz-slate member 488 



Fig. 1. Qnartzite. 



Fig. 2. The same, in polarized light. 

 Fig. 3. Fernigiuons <inartzite. 

 Fig. 4. The same, in polarized light. 

 XXI. Thin sections of sideritii' loclis ironi the Iron-bearing member and from Law- 

 rence connty, Ohio 490 



Fig. 1. Sideritic chert. 



Fig. 2. The same, in polarized light. 



Fig. 3. Sideritic slate. 



Fig. 4. Sideritic and ferriiginou,s chert. 



XXII. Thin sections of ferruginons cherts from the Iron-bearing member 493 



Fig. 1. C'oncretion.ary i liert. 



Fig. 2. The same, in polHrized llglit. 



Fig. 3. Brecciated chert. 



Fig. 4. Ferrugin(nis and brecciated chert. 



XXIII. Thin sections of ferrnginons cherts and actluolitic slates from the Iron-bearing 



member — 494 



Fig. 1. Ferriiginons cliert. 



Fig. 2. The same, in polarized liglit. 



Fig. 3. Actinolitic schist. 



Fig. 4. The same, in j)olarized light. 



XXIV. Tliiu sections of the actinolitic slates from tlie Iron-bearing member of the 



Penokee series, and cherty iron carbonates from the Vermillion series 496 



Fig. 1. Actiuolite-magnetite-schist. 



Fig. 2. Actinolitic slate. 



Fig. 3. Cherty iron carbonate. 



Fig. 4. Tlie same, in polarized liglit. 



XXV. Thin .sections of sideritic slates from the Animikie series 498 



Fig. 1. Cherty iron carbonate. 

 Fig. 2. Sideritic chert. 

 Fig. 3. Aetinolite-siderite-slate. 

 Fig. 4. The same, in polarized light. 

 XXVI. Thin sections of ferruginous crlierts and iron carbonates from the Animikie 



series ^00 



Fig. 1. Concretionary <hert. 

 Fig. 2. The same, in polarize<l light. 

 Fig. 3. Ferrnginons chert. 

 Fig. 4. Sideritic chert. 



XXVII. Til in sections showing formation of «oncretions of Iroii-liearing member 502 



Fig. 1. Sideritic chert. 



Fig. 2. Siileritic chert. 



Fig. 3. Another jiart of the same section. 



Fig. 4. Ferruginous rhcit. 



